I am big fan of Game Maker (see link) as intro language for 9-12 years old to programming. You need to try it to believe it: totally GUI drag'n'drop interface to program real playable fun games within an hour - using very high level language oriented for games. 99% of the time you don't need to write any code - all is filling event slots for each object by lego-like constructs (with intuitive icons). Perfect for kids learning to create first programs, learning IF, LOOP, EVENT, CREATE/DELETE object, timers, status etc. All these are objects with intuitive icons, easy to understand.

Overmars has very intuitive GUI to do it, sry windows only. games for 2 players (using different parts of the keyboard to navigate) are possible too.

My experience tells me it is perfect tool to hook youngsters to programming - more fun than writing boring lines in python which only write text output. Seduce them on Linux and Python :-) I will be happy to give you more info about GM - email me if interested. Thanks.